Improved Nyquist Filters Research Articles

Construction of new ISI-free pulses using a linear combination of two polynomial pulses

This paper deals with the design of inter-smybol interference free pulses having reduced sensitivity to time synchronization errors. A new improved Nyquist filter is proposed and investigated. Its impulse response is obtained from a linear combination of new Nyquist pulses with different asymptotical decay rates. Error probability results show that the proposed filter outperforms other existing filters. The proposed scenarios aimed at demonstrating the feasibility of the concept.

Investigation of the mechanism of improvement in improved Nyquist filters

In this study, the authors have investigated the mechanism that determines improved Nyquist filters (INFs) to perform better in the presence of timing errors. The authors have explored the role of low- and high-frequency regions in the range [B(1 − α), B], where B is the bandwidth corresponding to T = 1/2B in producing a smaller error probability in the presence of symbol timing error. The authors first have analysed the performance of the POWER pulse and evidenced the role of the slope of the frequency characteristic in the vicinity of B(1 − α), determined the optimal values of the exponent β and derived a formula that links β and the slope value at B(1 − α + α/100) to the normalised time offset. Then, the authors have proposed five new INFs with piece-wise polynomial frequency characteristic, and investigated the influence of component frequency bands and shapes on the error probability, when the impulse response is sampled with a time offset. The authors consider that the slope of the frequency characteristic in the transition band in the vicinity of B(1 − α) has a direct effect on the error probability. Finally, the authors have presented the performance evaluation and practical engineering challenges brought in by the use of the new pulses in an N-subcarrier orthogonal frequency-division multiplexing (OFDM) systems in order to reduce inter-carrier interference power.

Improved Nyquist Pulses Produced By A Filter with Senary Piece-wise Polynomial Frequency Characteristic

A novel family of inter-symbol interference (ISI) free pulses generated by improved Nyquist filters with a frequency characteristic composed of six parabolic pieces is proposed. We stud ...

Two improved nyquist filters with piece-wise rectangular-polynomial frequency characteristics

In this article a novel method for constructing a family of improved Nyquist filters is provided, as well as some guidelines on how the inter-symbol interference (ISI) problem can be approached. The proposed solution for the design of Nyquist pulses is based on a piece-wise rectangular-polynomial frequency characteristic using second and third degree polynomials. The characteristic property of the novel family of ISI-free pulses generated by the proposed filters is the asymptotic decay rate of t−2. By introducing this approach, comparable or better results are obtained in terms ISI performance as compared to several recently proposed pulses.

Improved Nyquist Filters with Piece-Wise Parabolic Frequency Characteristics

This paper presents and investigates a novel approach for constructing a family of ISI-free pulses having an asymptotic decay rate of t <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , and comparable or better ISI performance as compared to several recently proposed pulses. The proposed solution for the design of Nyquist pulses is based on a piece-wise parabolic frequency characteristic. This can be considered as a piece-wise polynomial frequency characteristic with second degree polynomials. It is shown that a lower bit error rate (BER) can be achieved for same values of the roll-off factor, timing jitter, signal to noise ratio and number of interfering pulses, as compared to recently reported pulses.

ISI-free pulses produced by improved Nyquist filter with piece-wise linear characteristic

A family of improved Nyquist filters with a piece-wise rectangular frequency characteristic composed of six nonzero linear segments with variable-length projections onto the frequency axis is investigated. They produce a family of inter-symbol interference-free (ISI-free) pulses with an asymptotic decay rate of t−2 that shows comparable or better inter-symbol interference performance, compared with some recently proposed pulses. The co-ordinates of the points that delimit the linear segments are varied in a limited interval in order to obtain a minimum value of the probability of error when the impulse response is sampled with a small time offset. The results outperform previously reported pulses taken as a reference.

Improved Nyquist filter with an ideal piece-wise rectangular characteristic

The present approach is centered on the optimization of a piece-wise rectangular transfer characteristic in order to obtain a minimal value of the error probability when the impulse response is sampled with small timing errors. We proposed a new parametric method for the design of the Nyquist filter using constraints in the frequency characteristic construction. We studied the family of new Nyquist filters based on a composite frequency characteristic and investigated its performances in terms of ISI error probability. This method of construction allows us to derive improved Nyquist filters in terms of ISI error probability. We also observed the variation of the side lobes of the pulses when a larger number of parameters is introduced in the proposed filter frequency characteristic. An implementation example of a real filter with improved performance in terms of ISI error probability when sampled with small timing errors is presented.

A Comparison of Double Convex and Double Concave Improved Nyquist Filters

This paper presents a comparative analysis of two families of improved Nyquist filters with a piece-wise parabolic frequency characteristic. Their construction is based on a novel ap ...

Improved Nyquist filter characteristics using spline interpolation

This paper presents and investigates a novel approach for constructing a family of intersymbol interference (ISI)-free pulses that shows comparable or better ISI performance in the presence of sampling errors, compared with some recently proposed pulses. We propose and discuss a new parametric method for the design of Nyquist filter characteristics using constraints in frequency characteristics construction. The method for constructing the filter characteristics uses a piecewise polynomial approximation of an ideal optimized staircase characteristic by spline functions. The spline polynomials are used to approximate a function that must pass through specified points. The performances of new ISI-free pulses are studied with respect to the ISI error probability. This family provides flexibility in designing an appropriate pulse even after the roll-off factor has been chosen. The results for error probability outperform the fourth-degree polynomial pulse [4].

Improved Nyquist Filters with a Transfer Characteristic Derived from a Staircase Characteristic Interpolated with Sine Functions

This paper investigates a novel approach forconstructing a family of ISI-free pulses produced by improvedNyquist filters with a transfer characteristic derived from anideal stairca ...